The article “Global Corneal Blindness and the Boston Keratoprosthesis Type 1” by Ament and associates illustrates the substantial global burden of visual impairment and the relief of this burden afforded by the use of the Boston keratoprosthesis type 1. As the authors reported, more than 1 million people in China are corneal blind, and most live in rural areas. Although the first Boston keratoprosthesis type 1 implantation in China was performed in 2004 as a part of an Orbis International training program, a keratoprosthetic of similar design to the Boston type 2 already was under development.
The keratoprosthesis used in our hospital was developed by the Moscow Eye Microsurgery Complex in Russia, hence its name, the MICOF keratoprosthesis. The MICOF keratoprosthesis is composed of a central rigid polymethyl methacrylate optical cylinder (diameter, 2.5 mm) and a titanium frame. The cylinder length is 2.2 to 2.4 mm, according to corneal thickness. The range of diopter is +55.00 to +62.00. Optical power is selected according to axial length as measured by A-scan ultrasonography. The MICOF keratoprosthesis is similar to the Boston type 2 keratoprosthesis in that both are used in cicatrizing corneal diseases with poor tear function like Stevens-Johnson syndrome, ocular cicatricial pemphigoid, and severe chemical burns. Both have an optical portion consisting of 2 plates joined by a stem. The most significant difference may be that donor graft is not used in the MICOF keratoprosthesis. MICOF keratoprosthesis implantation is carried out using a 2-stage surgical procedure performed over 3 months. In stage 1, a supporting titanium frame is inserted into the lamellar pocket; a polymethyl methacrylate optical cylinder is implanted 3 months later in stage 2. Both surgeries are performed under retrobulbar anesthesia.
The MICOF keratoprosthesis has been used in our hospital since 1999 on more than 100 patients, most commonly for chemical burns. Visual rehabilitation is significant. Most patients achieve visual acuity better than 20/100 at 6 months after stage 2. The retention rate is more than 80% (unpublished data). Retroprosthetic membrane formation and glaucoma are the most common complications. Because much of China’s population is rural, it is difficult for patients to return for postoperative care. Compared with the Boston keratoprosthesis type 1, the MICOF keratoprosthesis may be cheaper. Although the MICOF keratoprosthesis is considered only in instances of poor prognosis for keratoplasty, it is a promising development for such patients in China.